Curable resin composition

ABSTRACT

The present invention provides a composition, which is easy to produce because of high ease of handling the starting materials. The composition exhibits excellent transparency, and a product prepared using the composition exhibits excellent mechanical properties and adhesive properties. 
     The curable resin composition contains (A) an oxyalkylene polymer having silicon-containing functional groups crosslinkable through formation of siloxane bonds; (B) a copolymer having silicon-containing functional groups crosslinkable through formation of siloxane bonds, the molecular chain of the copolymer consisting substantially of (b-1) an alkyl (meth)acrylate monomeric unit having C 1 –C 2  alkyl and (b-2) an alkyl (meth)acrylate monomeric unit having C 7 –C 9  alkyl; and (C) a curing agent.

This is a National Stage of International Application No. PCT/JP02/10977filed Oct. 23, 2002, claiming priority to Japanese Application No. 2001-324676 filed on Oct. 23, 2001.

TECHNICAL FIELD

The present invention relates to a curable composition containing atleast two curable polymers. In particular, it relates to a curablecomposition containing a crosslinkable alkyl (meth)acrylate polymer anda crosslinkable oxyalkylene polymer. In the present invention, the term“alkyl (meth)acrylate” refers to “alkyl acrylate and/or alkylmethacrylate”.

BACKGROUND ART

A curable composition containing an oxyalkylene polymer havingsilicon-containing functional groups crosslinkable through the formationof siloxane bonds (hereinafter, simply referred to as “reactive silicongroups”) and, optionally, an alkyl (meth)acrylate polymer containingreactive silicon groups is disclosed in, for example, JapaneseUnexamined Patent Application Publication Nos. 59-122541, 60-31556,63-112642, and 6-172631.

Among these publications, Japanese Unexamined Patent ApplicationPublication No. 63-112642 discloses a composition containing a copolymercontaining long-chain alkyl (meth)acrylate. This composition has variouspractical characteristics, such as transparency and tensile properties,superior to those of other compositions disclosed in the otherpublications described above. However, long-chain alkyl (meth)acrylatemonomers, i.e., the starting material of the copolymer containinglong-chain alkyl (meth)acrylate, are generally expensive and aredifficult to handle since long-chain alkyl (meth)acrylate monomers aresolid at room temperature. Moreover, in a typical process used tosynthesize a copolymer containing alkyl (meth)acrylate monomeric unitsby polymerization, the monomeric unit must be cooled in advance for thesafety reasons. Long-chain alkyl (meth)acrylate monomers tend toprecipitate when mixed with other monomeric units cooled in advance,which is a problem. In general, alkyl (meth)acrylate polymers exhibit ahigher glass transition temperature, larger cohesive force, and higherviscosity than those of oxyalkylene polymers. Thus, the viscosity of acomposition containing an oxyalkylene polymer and an alkyl(meth)acrylate polymer increases, which is problem from a practicalviewpoint.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a curable resincomposition, which is easy to produce since starting materials thereforare easy to handle. The curable resin composition exhibits excellenttransparency, and a product prepared from the curable resin compositionexhibits excellent mechanical properties and adhesive properties.

The Inventors have made the present invention based on the finding thatthe above-described object can be achieved by using a copolymercontaining an alkyl (meth)acrylate monomeric unit having C₁–C₂ alkyl andan alkyl (meth)acrylate monomeric unit having C₇–C₉ alkyl in preparing acurable resin composition containing an oxyalkylene polymer havingsilicon-containing functional groups crosslinkable through formation ofsiloxane bonds, a copolymer having silicon-containing functional groupscrosslinkable through formation of siloxane bonds, and a curing agent.

In particular, the present invention provides a curable resincomposition including (A) an oxyalkylene polymer havingsilicon-containing functional groups crosslinkable through formation ofsiloxane bonds; (B) a copolymer having silicon-containing functionalgroups crosslinkable through formation of siloxane bonds, the molecularchain of the copolymer consisting substantially of (b-1) an alkyl(meth)acrylate monomeric unit having C₁–C₂ alkyl and (b-2) an alkyl(meth)acrylate monomeric unit having C₇–C₉ alkyl; and (C) a curingagent.

In a preferred embodiment, the molecular chain of the polymer (A) issubstantially constituted from a repeating unit represented by generalformula (1):—CH(CH₃)CH₂—O—  (1)

In a more preferred embodiment, the number-average molecular weight ofthe polymer (A) of the curable resin composition is at least 6,000 andMw/Mn is 1.6 or less.

In a most preferred embodiment, the main chain of the polymer (A) of thecurable resin composition is synthesized by polymerizing alkylene oxidein the presence of an initiator and at least one catalyst selected fromthe group consisting of a cyanide complex of compound metal, a cesiumcompound, and a compound containing a P═N bond.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will now be described in detail.

Reactive silicon groups contained in the oxyalkylene polymer of acomponent A of the present invention are not particularly limited.Representative examples thereof include those represented by generalformula (2) below:—(—Si(R¹ _(2-b))X_(b)—O—)_(m)—Si(R² _(3-a))X_(a)  (2)(wherein R¹ and R² each represent a C₁–C₂₀ alkyl group, a C₆–C₂₀ arylgroup, a C₇–C₂₀ aralkyl group, or a triorganosiloxy group represented by(R′)₃SiO—; when two or more R¹s or R²s exist, they may be the same ordifferent; R′ represents a monovalent C₁–C₂₀ hydrocarbon group; thethree R's may be the same or different; X represents a hydroxy group ora hydrolyzable group; when two or more Xs exist, they may be the same ordifferent; a represents 0, 1, 2, or 3; and b represents 0, 1, or 2.Among the number m of the repeating units represented by general formula(3) in the formula, the value of b may be the same or different:—Si(R¹ _(2-b))X_(b)—O—  (3)wherein m represents an integer in the range of 0 to 19; and a+Σb≧1.)

The hydrolyzable group represented by X is not particularly limited. Anyknown hydrolyzable group can be suitably used. Examples of thehydrolyzable group include a hydrogen atom, a halogen atom, an alkoxylgroup, an acyloxy group, a ketoximate group, an amino group, an amidegroup, an acid amide group, an aminooxy group, a mercapto group, andalkenyloxy group. Among these, a hydrogen atom, an alkoxyl group, anacyloxy group, a ketoximate group, an amino group, an amide group, anaminooxy group, a mercapto group and an alkenyloxy group are preferredfor their influence to environment and ready availability of startingmaterials. In particular, an alkoxyl group such as a methoxy group ispreferred due to its moderate hydrolyzability and ease of handling.

One to three hydrolyzable groups or hydroxyl groups can bond with onesilicon atom. Preferably, (a+Σb) is in the range of 1 to 5. When two ormore hydrolyzable groups or hydroxyl groups exist in the reactivesilicon group, they may be the same or different. The number of siliconatoms in the reactive silicon group may one or more. When the reactivesilicon group has its silicon atoms linked through siloxane bonding,about twenty silicon atoms may be contained in the group. The type ofreactive silicon group is not particularly limited but is preferablyselected from a dimethylmonomethoxysilyl group, a methyldimethoxysilylgroup, a trimethoxysilyl group, an ethyldiethoxysilyl group, atriethoxysilyl group, a methyldiisopropenyloxysilyl group, and atriisopropenyloxysilyl group due to their high hydrolysis activity,moderate hydrolyzability, and ease of handling. Two or more of thesegroups may be included.

One polyalkylene polymer molecule preferably contains at least one, andmore preferably 1.1 to 5 reactive silicon groups. When the number ofreactive silicon groups is less than one per molecule, neithersufficient curability nor sufficient rubber elasticity can be obtained.When the number of reactive silicon groups is more than five, anexcessively hard product will result. The reactive silicon group mayexist at an end of or within the oxyalkylene polymer molecular chain.Reactive silicon groups preferably exist at the ends since the effectivecrosslinking density of the oxyalkylene polymer component contained inthe resulting cured product increases and the product can exhibit highstrength, high extensibility, and low elastic modulus as a result.

Nonlimiting examples of the oxyalkylene polymer, i.e., the component Aof the present invention, include polyoxyethylene, polyoxypropylene,polyoxybutylene, polyoxyisobutylene, and polyoxytetramethylene. Themolecular chain of the oxyalkylene polymer A may consist of one type ofrepeating unit or two or more types of repeating units. The oxyalkylenepolymer may be straight or branched, or both straight and branched.Among these oxyalkylene polymers, those having a molecular chainconsisting substantially of a repeating unit represented by generalformula (1) are particularly preferred since the curable compositionprepared therefrom can be easily handled and a cured product preparedfrom the curable composition exhibits satisfactory physical properties:—CH(CH₃)CH₂—O—  (1)Here, the term “substantially” means that the polymer may contain othermonomers but the repeating unit represented by formula (1) above shouldbe contained in an amount of at least 50 percent by weight andpreferably at least 80 percent by weight of the total of the monomericunits of the polymer A.

The polystyrene-equivalent number-average molecular weight (Mn) of theoxyalkylene polymer determined by gel permeation chromatography (GPC) ispreferably 6,000 to 60,000 and more preferably 8,000 to 50,000 toachieve sufficient curability and ease of handling. Most preferably, Mnis 10,000 to 30,000 to further achieve superior mechanical properties.The ratio of the weight-average molecular weight to the number-averagemolecular weight (Mw/Mn) in terms of polystyrene equivalent by GPC ispreferably 1.6 or less, more preferably 1.5 or less, and most preferably1.4 or less to yield a narrow molecular weight distribution (smallerMw/Mn). When mixed with a reactive-silicon-containing alkyl(meth)acrylate copolymer B, an oxyalkylene polymer A having such anarrow molecular distribution can produce a low-viscosity compositionthat can be worked easily compared to when an oxyalkylene polymer havinga broad molecular weight distribution is used.

The reactive-silicon-group-containing oxyalkylene polymer, i.e., thecomponent A, of the present invention can be prepared by, for example,introducing reactive silicon groups into an oxyalkylene polymer havingfunctional groups.

A known method may be employed to introduce reactive silicon groups.Examples of such methods are as follows:

-   (1) An oxyalkylene polymer having functional groups, such as hydroxy    groups, at the ends is reacted with an organic compound having    unsaturated groups and active groups reactive to these functional    groups, and the resulting reaction product is hydrosilylated using    hydrosilane having hydrolyzable groups; and-   (2) An oxyalkylene polymer having functional groups Y, such as    hydroxyl groups, epoxy groups, and isocyanate groups, at the ends is    reacted with a compound having a functional group Y′ reactive to the    functional groups Y and a reactive-silicon-group-containing    compound. Nonlimiting examples of the silicon compound having the    functional group Y′ include amino-group-containing silanes such as    γ-(2-aminoethyl)aminopropyltrimethoxysilane,    γ-(2-aminoethyl)aminopropylmethyldimethoxysilane, and    γ-aminopropyltriethoxysilane; mercapto-group-containing silanes such    as γ-mercaptopropyltrimethoxysilane and    γ-mercaptopropylmethyldimethoxysilane; epoxysilanes such as    γ-glycidoxypropyltrimethoxysilane, and    β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane;    vinyl-unsaturated-group-containing silane groups such as    vinyltriethoxysilane, γ-methacryloyloxypropyltrimethoxysilane, and    γ-acryloyloxypropylmethyldimethoxysilane; chlorine-containing    silanes such as γ-chloropropyltrimethoxysilane;    isocyanate-containing silanes such as    γ-isocyanatepropyltriethoxysilane and    γ-isocyanatepropylmethyldimethoxysilane; and hydrosilanes such as    methyldimethoxysilane, trimethoxysilane, and methyldiethoxysilane.

Among the methods described above, method (1) and method (2) with ahydroxy-terminated polymer reacted with a compound containing anisocyanate group or a reactive silicon group are particularly preferreddue to ease of obtaining the starting materials and carrying out thereaction.

Introduction of reactive silicon groups results in widening of themolecular weight distribution from that of the polymer before theintroduction. Accordingly, the molecular weight distribution of thepolymer before the introduction is preferably as narrow as possible.

The oxyalkylene polymer having a high molecular weight and a narrowmolecular weight distribution can be synthesized by, for example, themethods disclosed in Japanese Unexamined Patent Application PublicationNos. 61-197631, 61-215622, 61-215623, 61-218632, 50-149797, 61-197631,2-276821, 10-273512, 10-36499, 11-106500, and 11-302371 and in JapaneseExamined Patent Application Publication Nos. 46-27250, and 59-15336.

The oxyalkylene polymer is preferably prepared by polymerizing alkyleneoxide catalyzed by at least one compound selected from the groupconsisting of a cyanide complex of compound metal, a cesium compound,and a compound containing a P═N bond in the presence of an initiator. Inthis manner, a polymer having a narrow molecular weight distribution canbe easily obtained.

Examples of the initiator include dihydric alcohol and polyalcohol suchas ethylene glycol, propylene glycol, butanediol, hexamethylene glycol,methallyl alcohol, hydrogenated bisphenol A, neopentyl glycol,polybutadiene diol, diethylene glycol, triethylene glycol, polyethyleneglycol, dipropylene glycol, glycerin, trimethylolmethane,trimethylolpropane, and pentaerythritol; and various oligomerscontaining hydroxy groups. Among these examples, polypropylene glycol,polypropylene triol, and polypropylene tetraol are particularlypreferred due to their economical advantages and handling ease.

The cyanide complex of compound metal used in the present invention ispreferably a complex mainly containing zinc hexacyanocobaltate from thestandpoint of polymerization activity. More preferably, the cyanidecomplex is an ether and/or alcohol complex from the standpoint ofpolymerization control. In order to obtain a polymer with a narrowermolecular weight distribution, the ether is preferably ethylene glycoldimethyl ether (glyme) or diethylene glycol dimethyl ether (diglyme),and the alcohol is preferably t-butanol.

The amount of the cyanide complex of compound metal is preferably 0.0001to 0.03 percent by weight of the final polyoxyalkylene compound. Theamount is more preferably 0.001 to 0.01 percent by weight from thestandpoint of reactivity. At an amount less than 0.0001 percent byweight, the reaction rate is not sufficiently high. At an amountexceeding 0.03 percent by weight, the cost of making the polyoxyalkylenecompound increases.

The cesium compound of the present invention preferably contains one ofthe following as the primary material from the standpoint of reactivity:cesium metal; cesium alkoxide such as cesium methoxide, cesium ethoxide,and cesium propoxide; cesium hydroxide; and cesium carbonate. Cesiumhydroxide is particularly preferred due to its ready availability andeconomical advantages.

The amount of the cesium compound in terms of cesium metal is preferably0.05 to 1.5 percent by weight of the final polyoxyalkylene compound. Theamount is preferably 0.1 to 1.0 percent by weight from the standpoint ofreactivity. At an amount less than 0.05 percent by weight, a sufficientreaction rate cannot be achieved. At an amount exceeding 1.5 percent byweight, the cost of manufacturing the polyoxyalkylene compoundincreases.

In the present invention, the compound containing the P═N bond ispreferably at least one compound selected from the group consisting of aphosphazenium compound, a phosphine oxide compound, and a phosphazenecompound.

Examples of the phosphazenium compound are disclosed in JapaneseUnexamined Patent Application Publication No. 11-106500. In particular,the examples includetetraquis[tris(dimethylamino)phosphoranylideneamino]phosphoniumhydryoxide,tetraquis[tris(dimethylamino)phosphoranylideneamino]phosphoniummethoxide,tetraquis[tris(dimethylamino)phosphoranylideneamino]phosphoniumethoxide, andtetraquis[tri(pyrrolidin-1-yl)]phosphoranylideneamino]phosphoniumtert-butoxide.

Examples of the phosphazene compound are disclosed in JapaneseUnexamined Patent Application Publication No. 10-36499. In particular,the examples include 1-tert-butyl-2,2,2-tris(dimethylamino)phosphazene,1-(1,1,3,3-tetramethylbutyl)-2,2,2-tris (dimethylamino)phosphazene,1-ethyl-2,2,4,4,4-pentaquis(dimethylamino)-2λ5,4λ5-catenadi(phosphazene),1-tert-butyl-4,4,4-tris(dimethylamino)-2,2-bis[tris (dimethylamino)phosphoranylideneamino]-2λ5,4λ5-catenadi(phosphazene),1-(1,1,3,3-tetramethylbutyl)-4,4,4-tris(dimethylamino)-2,2-bis[tris(dimethylamino)phosphoranylideneamino]-2λ5,4λ5-catenadi(phosphazene),1-tert-butyl-2,2,2-tri(1-pyrrolidinyl)phosphazene, and7-ethyl-5,11-dimethyl-1,5,7,11-tetraaza-6λ5-phosphaspiro[5,5]undeca-1(6)-en.

Examples of the phosphine oxide compound are disclosed in JapaneseUnexamined Patent Application Publication No. 11-302371. In particular,the examples includetris[tris(dimethylamino)phosphoranylideneamino]phosphine oxide, andtris[tris(diethylamino)phosphoranylideneamino]phosphine oxide.

Among these compounds, the phosphazenium compound and the phosphineoxide compound are particularly preferred from the standpoint ofindustrial use.

The amount of the P═N bond-containing compound is preferably 1×10⁻⁴ to5×10⁻¹ mole per mole of active hydrogen compound in the initiator. At anamount less than 1×10⁻⁴ mole, the reaction rate is not sufficientlyhigh. At an amount exceeding 5×10⁻¹ mole, the cost of manufacturing thepolyoxyalkylene compound increases.

The (meth)acrylate monomeric unit having C₁–C₂ alkyl, which is acomponent b-1 of the component B, which is thereactive-silicon-containing alkyl (meth)acrylate copolymer (hereinaftersimply referred to as “the copolymer B”), is represented by generalformula (4):CH₂═C(R³)COOR⁴  (4)wherein R³ represents a hydrogen atom or a methyl group and R⁴represents a C₁–C₂ alkyl group. Examples of R⁴ include a methyl groupand an ethyl group. When the (meth)acrylate monomeric unit having C₁–C₂alkyl is used as the component b-1, a product exhibiting high bondstrength and superior rubber elasticity can be prepared from the curableresin composition of the present invention. The monomers represented bygeneral formula (4) may be used alone or in combination.

The (meth)acrylate monomeric unit having C₇–C₉ alkyl, which is acomponent b-2, is represented by general formula (5):CH₂═C(R⁵)COOR⁶  (5)wherein R⁵ represents a hydrogen atom or a methyl group and R⁶represents a C₇–C₉ alkyl group. Examples of R⁶ include alkyl groups suchas n-heptyl, isoheptyl, n-octyl, 2-ethylhexyl, isooctyl, n-nonyl, andisononyl. In particular, a 2-ethylhexyl group is preferred from thestandpoint of economy and availability of the starting materials. Themonomers represented by general formula (5) may be used alone or incombination.

When the (meth)acrylate monomeric unit having C₇–C₉ alkyl is used as thecomponent b-2, a composition having transparency comparable to that of aconventional composition can be prepared with higher ease of handlingthe monomeric units. Moreover, the cured product prepared from thecomposition of the present invention has rubber elasticity and bondstrength superior to conventional compositions.

The molecular chain of the copolymer B consists substantially of thecomponent b-1 and the component b-2, which are monomeric units. Here,the term “substantially” means that the total content of the componentsb-1 and b-2 exceeds 50 percent by weight and more preferably 70 percentby weight of the total amount of the copolymer B.

The weight ratio of the amount of the component b-1 to the total of theb-1 and b-2 components is preferably 95 percent by weight or less toimprove ease of handling the curable resin composition of the presentinvention and more preferably 85 percent by weight or less to improvethe bond strength. From the same standpoint, the ratio is preferably atleast 40 percent by weight and more preferably at least 50 percent byweight. When the ratio of the component b-1 exceeds 95 percent byweight, the resulting curable composition may become excessivelyviscous, thus complicating handling. When the ratio of the component b-1is less than 40 percent by weight, the adhesiveness to various substratematerials may be degraded.

The copolymer B may contain other monomeric units in addition to thecomponents b-1 and b-2. Examples of such monomeric units includemonomers having carboxylic groups such as acrylic acid and methacrylicacid; monomers having amide groups such as acrylamide, methacrylamide,N-methylolacrylamide, and N-methylolmethacrylamide; monomers havingepoxy groups such as glycidyl acrylate and glycidyl methacrylate;monomers having amino groups such as diethylaminoethyl acrylate,diethylaminoethyl methacrylate, and aminoethyl vinyl ether; and othermonomeric units based on acrylonitrile, styrene, α-methylstyrene,alkylvinylether, vinyl chloride, vinyl acetate, vinyl propionate, andethylene.

The polystyrene-equivalent number-average molecular weight of thecopolymer B is preferably 500 to 100,000, more preferably 7,000 to10,000, and most preferably 1,000 to 5,000 by GPC to simplify handling.When the number-average molecular weight of the copolymer B is less than500, the resulting product cannot exhibit sufficient rubber elasticity.When the number-average molecular weight of the copolymer B is more than100,000, the viscosity excessively increases, and handling becomes moredifficult.

The reactive silicon groups in the copolymer B are the same as those inthe oxyalkylene polymer A in the present invention and are crosslinkableat room temperature. Typical examples of the reactive silicon group arerepresented by general formula (6):—Si(R² _(3-a))X_(a)  (6)wherein R², X, and a are the same as above.

Specific examples of the reactive silicon groups in the copolymer B fromthe standpoint of economy and ease of handling include adimethylmonomethoxysilyl group, a methyldimethoxysilyl group, atrimethoxysilyl group, an ethyldiethoxysilyl group, a triethoxysilylgroup, a methyldiisopropenyloxysilyl group, and a triisopropenyloxysilylgroup. The reactive silicon groups of the copolymer B are preferably atleast one selected from these.

The average number of the reactive silicon group per molecule of thecopolymer B is at least 1, preferably at least 1.1, and more preferablyat least 1.5 to obtain sufficient curability. The apparentnumber-average molecular weight per reactive silicon group is preferably300 to 4,000.

The copolymer B of the present invention is synthesized through vinylpolymerization of the monomers b-1 and b-2. Examples of the vinylpolymerization include radical vinyl polymerization, e.g., typicalsolution polymerization and mass polymerization. The monomers, a radicalinitiator (optional), and a chain transfer agent (optional) foradjusting the molecular weight, such as n-dodecylmercaptan ort-dodecylmercaptan, may be polymerized at a reaction temperature of 50to 150° C. A solvent may be used if required. If a solvent is required,the solvent is preferably a nonreactive solvent such as ether,hydrocarbon, acetic acid ester, or alcohol since such a solvent isinexpensive and yields a safe polymerization reaction. From theenvironmental viewpoint, the solvent is preferably nonaromatic.Preferably, the nonaromatic solvent is an alcohol such as butanol fromthe environmental viewpoint and ease of handling the resulting polymer.

Various methods for introducing reactive silicon groups into thecopolymer B are available. Nonlimiting examples of the methods are asfollows: (I) a polymerization method including adding a compound, e.g.,CH₂═CHSi(OCH₃)₃, having polymerizable unsaturated bonds and reactivesilicon groups to the monomers b-1 and b-2; a method including adding acompound (such as acrylic acid) having polymerizable unsaturated bondsand reactive silicon groups (hereinafter simply referred to as “Zgroups”) to the monomers b-1 and b-2 to carry out copolymerization, andallowing the resulting copolymer to react with a compound havingfunctional groups (hereinafter “Z′ groups”) reactive with the Z groups,e.g., a compound having isocyanate groups and —Si(OCH₃)₃ groups; (III) amethod for copolymerizing the monomers b-1 and b-2 in the presence ofreactive-silicon-group-containing mercaptan functioning as a chaintransfer agent; (IV) a method for copolymerizing the monomers b-1 andb-2 using a reactive-silicon-group-containing azobisnitrile compound ora disulfide compound as the initiator; and (V) a method includingcopolymerizing the monomers b-1 and b-2 via a living radicalpolymerization and introducing reactive silicon groups at the ends ofthe molecular chain. The methods of (I) to (V) may be employed alone orin combination. For example, the methods of (I) and (III) may becombined to copolymerize the monomers b-1 and b-2 with the compoundhaving polymerizable unsaturated bonds and reactive silicon groups inthe presence of the reactive-silicon-group-containing mercaptanfunctioning as the chain transfer agent.

Specific examples of the compound used in method (I) includeCH₂═CHSi(CH₃)(OCH₃)₂, CH₂═CHSi(CH₃)Cl₂, CH₂═CHSi(OCH₃)₃, CH₂═CHSiCl₃,CH₂═CHCOO(CH₂)₂Si(CH₃)(OCH₃)₂, CH₂═CHCOO(CH₂)₂Si(OCH₃)₃,CH₂═CHCOO(CH₂)₂Si(CH₃)Cl₂, CH₂═CHCOO(CH₂)₂SiCl₃,CH₂═C(CH₃)COO(CH₂)₂Si(CH₃)(OCH₃)₂, CH₂═C(CH₃)COO(CH₂)₂Si(OCH₃)₃,CH₂═C(CH₃)COO(CH₂)₃Si(CH₃)(OCH₃)₂, CH₂═C(CH₃)COO(CH₂)₃Si(OCH₃)₃,CH₂═C(CH₃)COO(CH₂)₂Si(CH₃)Cl₂, CH₂═C(CH₃)COO(CH₂)₂SiCl₃,CH₂═CHCH₂OC(O)-Ph-COO(CH₂)₃Si(CH₃)(OCH₃)₂,CH₂═CHCH₂OC(O)-Ph-COO(CH₂)₃Si(OCH₃)₃,CH₂═CHCH₂OC(O)-Ph-COO(CH₂)₃Si(CH₃)Cl₂, andCH₂═CHCH₂OC(O)-Ph-COO(CH₂)₃SiCl₃, wherein Ph represents paraphenylene.Among these compounds, CH₂═CHSi(OCH₃)₃,CH₂═C(CH₃)COO(CH₂)₃Si(CH₃)(OCH₃)₂, and CH₂═C(CH₃)COO(CH₂)₃Si(OCH₃)₃ areparticularly preferred from the standpoint of economy and the reactivityof the resulting curable composition.

These silane compounds can be synthesized by various methods. Forexample, they can be prepared by reacting acetylene, allyl acrylate,allyl methacrylate, diallyl phthalate, or the like withmethyldimethoxysilane, methyldichlorsilane or the like in the presenceof a Group-VIII transition metal catalyst. For example, a Group-VIIItransition metal complex compound containing one selected from the groupconsisting of platinum, rhodium, cobalt, palladium, and nickel may beeffectively used as the catalyst. In particular, platinum compounds suchas platinum black, chloroplatinic acid, a platinum-alcohol compound, aplatinum-olefin complex, a platinum-aldehyde complex, and aplatinum-ketone complex are preferred.

Regarding the compound used in method (II), various combinations of theZ group and the Z′ group are possible. For example, the Z group can bevinyl and the Z′ group can be hydrosilicon (H—Si). The Z groups may bondwith the Z′ groups through hydrosilylation. Examples of the compoundhaving polymerizable unsaturated bonds and vinyl groups as the Z groupsinclude allyl acrylate and allyl methacrylate. Nonlimiting examples ofthe hydrosilane compound containing a hydrosilicon group as the Z′ groupand a reactive silicon group include alkoxysilanes such astrimethoxysilane, triethoxysilane, methyldiethoxysilane,methyldimethoxysilane, dimethylmethoxysilane, and phenyldimethoxysilane;acyloxysilanes such as methyldiacetoxysilane andtrimethylsiloxymethylacetoxysilane; ketoximatesilanes such asbis(dimethylketoximate)methylsilane,bis(cyclohexylketoximate)methylsilane, andbis(diethylketoximate)trimethylsiloxysilane; hydrosilanes such asdimethylsilane, trimethylsiloxymethylsilane, and1,1-dimethyl-2,2-dimethyldisiloxane; and alkenyloxysilanes such asmethyltri(isopropenyloxy)silane and dimethyltri(isopropenyloxy)silane.

Examples of the reactive-silicon-group-containing mercaptan used as thechain transfer agent of method (III) includeγ-mercaptopropyltrimethoxysilane, γ-mercaptopropylmethyldimethoxysilane,and γ-mercaptopropyltriethoxysilane. As is disclosed in JapaneseUnexamined Patent Application Publication No. 59-78222, a method ofcopolymerizing the monomers b-1 and b-2 in the presence of abifunctional radical-polymerizable compound and a chain transfer agent,i.e., alkoxysilyl-containing mercaptan, may be employed.

Examples of the reactive-silicon-group-containing azobisnitrile compoundor disulfide compound as the initiator used in method (IV) include analkoxysilyl-containing azobisnitrile compound and analkoxysilyl-containing disulfide compound disclosed in JapaneseUnexamined Patent Application Publication Nos. 60-23405 and 62-70405 andthe like.

An example method (V) is disclosed in Japanese Unexamined PatentApplication Publication No. 09-272714.

In addition, a method in which a radical polymerization initiator havingreactive silicon groups is used in combination with thereactive-silicon-group-containing mercaptan as disclosed in, forexample, Japanese Unexamined Patent Application Publication Nos.59-168014 and 60-228516 may also be employed.

Preferably, the curable composition of the present invention contains 5to 5,000 and more preferably 5 to 2,000 parts by weight (hereinafter,simply referred to as “parts”) of the copolymer B per 100 parts of theoxyalkylene polymer A so that both the polymer A and the copolymer B cansufficiently improve the characteristics. The ratio of the copolymer Bto the polymer A is generally selected according to the intended usageand performance.

A curing agent used as a component C of the present invention may be anysuitable one. Examples of a tin-based catalyst for use as the curingagent include bivalent tin carboxylates such as tin octylate, tinoleate, and tin stearate; dibutyltin dicarboxylates such as dibutyltindilaurate and dibutyltin bis(alkylmaleate); alkoxide derivatives ofdialkyltin such as dibutyltin dimethoxide and dibutyltin diphenoxide;intramolecular ligation derivatives such as dibutyltin diacetylacetonatoand dibutyltin acetoacetate; and derivatives of quadrivalent dialkyltinoxide such as a reaction mixture of dibutyltin oxide and an estercompound, a reaction mixture of dibutyltin oxide and a silicatecompound, and oxy derivatives of these dialkyltin oxide derivatives.Examples of a non-tin catalyst for use as the curing agent include metalcarboxylates such as calcium carboxylate, zirconium carboxylate, ironcarboxylate, vanadium carboxylate, bismuth carboxylate, leadcarboxylate, titanium carboxylate, and nickel carboxylate, each of whichcontains octyl acid, oleic acid, naphthenic acid, stearic acid, or thelike as the carboxylate component; titanium alkoxides such astetraisopropyl titanate, tetrabutyl titanate, tetramethyl titanate, andtetra(2-ethylhexyltitanate); aluminum alkoxides such as aluminumisopropylate, mono-sec-butoxy aluminum diisopropylate, andaluminum-sec-butyrate; zirconium alkoxides such as zirconium n-propoxideand zirconium n-butylate; titanium chelates such as titaniumtetraacetylacetonate, titanium ethylacetoacetate, octylene glycolate,and titanium lactate; aluminum chelates such as aluminumtrisacetylacetonate, aluminum trisethylacetoacetate, and diisopropoxyaluminum ethylacetoacetate; zirconium chelates such as zirconiumtetraacetylacetonato, zirconium monoacetylacetonato, zirconiumbisacetylacetonato, zirconium acetylacetonato bisethylacetoacetate, andzirconium acetate; and basic compounds such as amines, amine salts,quaternary ammonium salts, and quanidine compounds.

Among these, the tin-based catalysts are preferred in view of thereactivity of the curable composition. In particular, the followingcatalysts are preferred from the standpoint of economy and reactioncontrollability: dibutyltin dicarboxylates such as dibutyltin dilaurateand dibutyltin bis(alkylmaleate); alkoxide derivatives of dialkyltinsuch as dibutyltin dimethoxide and dibutyltin diphenoxide;intramolecular ligation derivatives such as dibutyltin diacetylacetonatoand dibutyltin acetoacetate; and derivatives of quadrivalent dialkyltinoxide such as a reaction mixture of dibutyltin oxide and an estercompound, a reaction mixture of dibutyltin oxide and a silicatecompound, and oxy derivatives of these dialkyltin oxide derivatives. Thecuring agent is normally selected according to the intended usage andtarget performance.

The amount of the curing agent is preferably 0.1 to 10 parts per a totalof 100 parts of the reactive-silicon-group-containing oxyalkylenepolymer A and the reactive-silicon-containing alkyl (meth)acrylatecopolymer B. When the amount of the curing agent is less than 0.1 part,the cure rate may become low and insufficient curing may result. At anamount exceeding 10 parts, heat or bubbles would be locally generatedduring curing, thereby producing a cured product with low quality.

In using the curable resin composition of the present invention, afiller may be added if required. Examples of the filler includereinforcing fillers such as fumed silica, precipitated silica, silicicanhydride, hydrous silica, and carbon black; fillers such as calciumcarbonate, magnesium carbonate, diatomite, calcined clay, clay, talk,titanium oxide, bentonite, organic bentonite, ferric oxide, zinc oxide,active zinc oxide, hydrogenated caster oil, and Shirasu balloon; andfibrous fillers such as asbestos, glass fibers, and filaments. When ahigh-strength cured product is desired, 1 to 100 parts of a fillerselected from fumed silica, precipitated silica, silicic anhydride,hydrous silica, carbon black, surface-treated fine calcium carbonate,calcined clay, clay, and active zinc oxide is preferably used relativeto a total of 100 parts of the reactive-silicon-group-containingoxyalkylene polymer A and the reactive-silicon-containing alkyl(meth)acrylate copolymer B. When a low-strength high-extensibilityproduct is desired, 5 to 200 parts of a filler selected from titaniumoxide, calcium carbonate, magnesium carbonate, talk, ferric oxide, zincoxide, and Shirasu balloon is preferably used relative to a total of 100parts of the reactive-silicon-group-containing oxyalkylene polymer A andthe reactive-silicon-containing alkyl (meth)acrylate copolymer B. Thesefillers can be used alone or in combination.

The curable resin composition of the present invention preferablycontains both a plasticizer and a filler since the extensibility of thehardened product can be increased and a large amount of filler can beused. Examples of the plasticizer include phthalic esters such asdioctyl phthalate, dibutyl phthalate, and butylbenzyl phthalate; acrylpolymer plasticizers such as a (meth)acryl polymer having a molecularweight distribution (Mw/Mn) of 1.8 or less prepared by living radicalpolymerization disclosed in Japanese Unexamined Patent ApplicationPublication No. 2000-178456 and the like, and a SGO polymer manufacturedby Toagosei Co., Ltd., set forth in Kogyo Zairyo (Engineering Materials)August 1998, p. 110; aliphatic dibasic acid esters such as dioctyladipate, isodecyl succinate, and dibutyl sebacate; glycol esters such asdiethylene glycol dibenzoate and pentaerythritol ester; aliphatic esterssuch as butyl oleate and methyl acetylricinolate; phosphate esters suchas tricresyl phosphate, trioctyl phosphate, and octyldiphenyl phosphate;epoxy plasticizers such as epoxidized soybean oil, epoxidized linseedoil, and benzyl epoxystearate; polyester plasticizers such as polyestersof dibasic acid and dihydric alcohol; polyethers such as polypropyleneglycol and derivatives thereof; polystyrenes such aspoly-α-methylstyrene and polystyrene; polybutadiene,butadiene-acrylonitrile copolymers, polychloroprene, polyisoprene,polybutene, and chlorinated paraffins. These plasticizers can be usedalone or in combination. Preferably, 0 to 100 parts of plasticizers isused relative to a total of 100 parts ofreactive-silicon-group-containing oxyalkylene polymer A and thereactive-silicon-containing alkyl (meth)acrylate copolymer B.

If necessary, various additives, such as a dehydrating agent, antackifier, an adhesion improving agent, an agent for adjusting physicalcharacteristics, a storage capacity improver, an antioxidant, a UVabsorber, a metal deactivator, an antiozonant, a light stabilizer, anamine radical crosslinking inhibiter, a decomposer for phosphorusperoxides, a slip additive, a pigment and a foaming agent, may be addedto the composition. The method for producing the curable composition ofthe present invention is not particularly limited. A common method, suchas mixing and kneading the above-described components using a mixer,rollers, or a kneader under normal or high temperature or dissolving andmixing the above-described components using a small amount of a suitablesolvent, may be employed. These components may be used in combination toprepare a one-component or a two-component composition.

Once exposed to air, the curable resin composition of the presentinvention forms a three-dimensional network structure and cures into asolid having rubber elasticity due to the presence of water. The curablecomposition of the present invention is particularly suitable for use inelastic sealants for construction, vessels, automobiles, and roadapplications. Moreover, since the curable resin composition alone or incombination with a primer can adhere to a wide range of base materialssuch as glass, ceramic, woods, metals, and molded resin, the curableresin composition of the present invention is applicable to varioussealing compositions and adhesive compositions. Examples of adhesiveapplications include a one-component adhesive, a two-component adhesive,a contact adhesive in which adhesion is completed after open time, and apressure sensitive adhesive. Moreover, the curable resin composition issuitable for use in paints, membrane-waterproofing agents, foodpackaging materials, cast rubber materials, molding materials, and foammaterials.

BEST MODES FOR CARRYING OUT THE INVENTION

The present invention will now be specifically described by way ofnonlimiting examples.

SYNTHETIC EXAMPLE 1

A polyoxypropylene glycol was prepared by polymerizing propylene oxidein the presence of a zinc hexacyanocobaltate glyme complex catalystusing an initiator, i.e., polyoxypropylene glycol having anumber-average molecular weight of about 2,000 determined by OH endgroup analysis. Methanol was then removed by adding 1.2 equivalents of aNaOMe methanol solution relative to the hydroxy groups of thishydroxyγ-terminated polyether oligomer. Subsequently, 3-chloro-1-propenewas added to transform the hydroxy groups at the ends into allyl groups.To 500 g of the resulting oligomer, 10 g of hexane was added, and theresulting mixture was dehydrated by azeotropic distillation at 90° C.After removing the hexane under reduced pressure, the oligomer waspurged with nitrogen. To the resulting mixture, 30 μl of aplatinum-divinyldisiloxane complex (3 wt. % isopropanol solution on aplatinum basis) was added, and 9.0 g of dimethoxymethylsilane (DMS) wasslowly added dropwise to the resulting mixture with stirring. Theresulting mixed solution was allowed to react for 2 hours at 90° C.Unreacting DMS was removed under a reduced pressure to obtain areactive-silicon-group-containing polyoxypropylene polymer. The ¹H-NMRanalysis of the polymer confirmed that the ratio of introducing reactivesilicon groups to the ends was 77% (polymer A). Thepolystyrene-equivalent number-average molecular weight (Mn) of thispolymer determined by GPC was about 15,000 and Mw/Mn was 1.1.

SYNTHETIC EXAMPLE 2

To a nitrogen-purged pressure glass reactor, 450 g of polyoxypropyleneglycol having a number-average molecular weight of about 3,000 and 50 gof polyoxypropylene triol having a number-average molecular weight of3,000 were charged. Methanol was removed from the mixture by adding 0.9equivalent of a NaOMe methanol solution relative to the end hydroxygroups of this oligomer. To the resulting mixture, 12 g of methylenechloride was added and the mixture was allowed to react at 130° C. Thevolatile components were removed from the mixture and then methanol wasremoved from the mixture by adding a NaOMe methanol solution.Subsequently, 15 g of 3-chloro-1-propene was added to transform the endhydroxyl groups to allyl groups. Upon completion of reaction, volatilecomponents were removed under a reduced pressure, and the reactionproduct was discharged into a beaker. The product was then dissolved inhexane, and the hexane was removed by adsorption using 150 g of aluminumsilicate under a reduced pressure. To 500 g of the resulting oligomer,10 g of hexane was added, and the mixture was dehydrated by azeotropicdistillation at 90° C. After removing the hexane under a reducedpressure, the mixture was purged with nitrogen and was then mixed with30 μl of platinum-divinyldisiloxane complex (3 wt % isopropanol solutionon a platinum basis). While the mixture was stirred, 11 g of DMS wasslowly added dropwise. After the mixed solution was allowed to react for2 hours at 80° C., unreacting DMS was removed under a reduced pressureto obtain a reactive-silicon-group-containing polyoxypropylene polymer.The ¹H-NMR analysis of the polymer confirmed that the ratio ofintroducing reactive silicon groups to the ends was 72% (polymer B). Thepolystyrene-equivalent number-average molecular weight (Mn) of thispolymer determined by GPC was about 19,000 and Mw/Mn was 1.9.

SYNTHETIC EXAMPLE 3

To prepare a mixture, 2.6 g of a polymerization initiator, i.e.,azobis-2-methylbutyronitrile, was added to a solution containing 66 g ofmethyl methacrylate, 19 g of 2-ethylhexyl acrylate, 5.4 g ofγ-methacryloxypropylmethyldimethoxysilane, 7.0 g ofγ-mercaptopropylmethyldimethoxysilane, and 23 g of toluene. The liquidmixture was added dropwise to 43 g of toluene, which was heated to 105°C., over 4 hours, and the mixture was allowed to react for two hours toprepare a polymer having a solid content of 60% and apolystyrene-equivalent number-average molecular weight (Mn) of 1,900determined by GPC (Polymer C).

SYNTHETIC EXAMPLE 4

To prepare a mixture, 2.6 g of a polymerization nitiator, i.e.,azobis-2-methylbutyronitrile, was added to a solution containing 72 g ofmethyl methacrylate, 18 g of 2-ethylhexyl acrylate, 4.0 g ofγ-mercaptopropylmethyldimethoxysilane, 4.0 g of normal dodecylmercaptan,and 23 g of toluene. The liquid mixture was added dropwise to 43 g oftoluene, which was heated to 105° C., over 4 hours, and the mixture wasallowed to react for two hours to prepare a polymer having a solidcontent of 60% and a polystyrene-equivalent number-average molecularweight (Mn) of 1,600 determined by GPC (Polymer D).

COMPARATIVE SYNTHETIC EXAMPLE 1

To prepare a mixture, 2.6 g of a polymerization initiator, i.e.,azobis-2-methylbutyronitrile, was added to a solution containing 72 g ofmethyl methacrylate, 18 g of stearyl methacrylate, 4.0 g ofγ-mercaptopropylmethyldimethoxysilane, 4.0 g of normal dodecylmercaptan,and 23 g of toluene. The liquid mixture was added dropwise to 43 g oftoluene, which was heated to 105° C., over 4 hours, and the mixture wasallowed to react for two hours to prepare a polymer having a solidcontent of 60% and a polystyrene-equivalent number-average molecularweight (Mn) of 1,800 determined by GPC (Polymer E).

COMPARATIVE SYNTHETIC EXAMPLE 2

To prepare a mixture, 2.6 g of a polymerization initiator, i.e.,azobis-2-methylbutyronitrile, was added to a solution containing 72 g ofmethyl methacrylate, 18 g of butyl acrylate, 4.0 g ofγ-mercaptopropylmethyldimethoxysilane, 4.0 g of normal dodecylmercaptan,and 23 g of toluene. The liquid mixture was added dropwise to 43 g oftoluene, which was heated to 105° C., over 4 hours, and the mixture wasallowed to react for two hours to prepare a polymer having a solidcontent of 60% and a polystyrene-equivalent number-average molecularweight (Mn) of 1,600 determined by GPC (Polymer F).

COMPARATIVE SYNTHETIC EXAMPLE 3

To prepare a mixture, 2.6 g of a polymerization initiator, i.e.,azobis-2-methylbutyronitrile, was added to a solution containing 66 g ofbutyl acrylate, 19 g of 2-ethylhexyl acrylate, 5.4 g ofγ-methacryloxypropylmethyldimethoxysilane, 7.0 g ofγ-mercaptopropylmethyldimethoxysilane, and 23 g of toluene. The liquidmixture was added dropwise to 43 g of toluene, which was heated to 105°C., over 4 hours, and the mixture was allowed to react for two hours toprepare a polymer having a solid content of 60% and apolystyrene-equivalent number-average molecular weight (Mn) of2,100-determined by GPC (Polymer G).

EXAMPLE 1

The oxyalkylene polymer (Polymer A) prepared in SYNTHETIC EXAMPLE 1 wasblended with the copolymer (Polymer C) prepared by SYNTHETIC EXAMPLE 3at a solid content ratio (weight ratio) of 60/40. The volatilecomponents of the resulting mixture were removed using an evaporatorunder a reduced pressure at a temperature of 110° C. to obtain acomposition having a solid content of 99% or more. The composition wasblended with a curing agent, i.e., U-220 manufactured by Nitto KaseiCo., Ltd., and predetermined amounts of a dehydrating agent and anadhesion-inducing agent described in Table 1 to prepare a curable resincomposition of the present invention. In Table 1, the content of eachcomponent of the composition is described in terms of parts by weight.

EXAMPLE 2

A curable resin composition of the present invention was prepared as inEXAMPLE 1 except that the polymer (Polymer B) prepared in SYNTHETICEXAMPLE 2 was used as the oxyalkylene polymer.

EXAMPLE 3

A curable resin composition of the present invention was prepared as inEXAMPLE 1 except that the polymer (Polymer D) prepared in SYNTHETICEXAMPLE 4 was used as the oxyalkylene polymer.

COMPARATIVE EXAMPLES 1 TO 3

The curable resin compositions of COMPARATIVE SYNTHETIC EXAMPLES 1 to 3were prepared as in EXAMPLE 1 except that the copolymers (Polymers E, F,and G) prepared in COMPARATIVE SYNTHETIC EXAMPLE 1 to 3 were usedrespectively as the copolymer.

The transparency of the resulting curable resin compositions wasvisually observed.

Each curable resin composition was formed into a 3-mm sheet, left tostand at 23° C. for three days, and heated at 50° C. for four days toprepare a rubbery sheet. A Japanese Industrial Standards (JIS) #3dumbbell piece was punched out from the rubbery sheet to determine thetensile properties, the modulus at 100% elongation, the elongation atbreak, and the strength.

Each curable resin was mixed with a filler, i.e., calcium carbonate (CCRmanufactured by Shiraishi Kogyo Kabushiki Kaisha). The amount of thecalcium carbonate was 50 parts with respect to a total of 100 parts ofthe component A and the component B of the present invention. Theresulting mixture was applied onto an aluminum plate (A-1050P, a100×25×2 mm test piece) to form a coating having a thickness of 0.05 mm.The coating was left to stand for 14 days at 23° C. and 50% R.H. to curethe coating. The tensile bond shear strength was then determined.

The ease of handling of the monomers in producing the copolymers wereevaluated as follows: “Good” when all monomers were liquid at roomtemperature and easily mix with each other during production, and “Poor”when some of the monomers were solid at room temperature and requiredheating to melt the monomers in mixing the monomers.

The results are shown in Table 1.

TABLE 1 EX. 1 EX. 2 EX. 3 C. EX. 1 C. EX. 2 C. EX. 3 Component Polymer A60 — 60 60 60 60 A Polymer B — 60 — — — — Component Polymer C 40 40 — —— — B Polymer D — — 40 — — — Polymer E — — — 40 — — Polymer F — — — — 40— Polymer G — — — — — 40 Component C *1 2 2 2 2 2 2 Dehydrating agent 33 3 3 3 3 *2 Tackifier *3 2 2 2 2 2 2 Handling ease of Good Good GoodPoor Good Good monomers in producing component B Transparency ofTransparent Transparent Transparent Transparent Phase Transparentcurable Separation composition Dumbbell 100% 0.25 0.23 0.09 0.09 — 0.27characteristics of modulus cured product (Mpa) Elongation 255 270 780760 — 140 at break (%) Strength 1.27 1.33 0.56 0.54 — 0.36 at break(MPa) Tensile bond shear 7.1 6.7 5.4 4.9 — 5.2 strength (MPa) *1: U-220,dibutyltin diacetylacetonato manufactured by Nitto Kasei Co., Ltd. *2:A171, vinyltrimethoxysilane manufactured by Nippon Unicar CompanyLimited. *3: A1122, γ-(2-aminoethyl)aminopropyltrimethoxysilanemanufactured by Nippon Unicar Company Limited.

The properties of the curable composition of COMPARATIVE EXAMPLE 2 werenot determined due to the occurrence of phase separation.

Table 1 shows that the curable resin compositions of EXAMPLES 1 to 3 areeasy to handle while achieving a transparency comparable or superior tothat of COMPARATIVE EXAMPLES 1 and 3. Moreover the mechanical propertiesand adhesive properties of cured products prepared from the resincompositions of EXAMPLES 1 to 3 are excellent.

INDUSTRIAL APPLICABILITY

A curable resin composition of the present invention is easy to producesince starting materials therefor are easy to handle. The curable resincomposition exhibits excellent transparency, and a product prepared fromthe curable resin composition exhibits excellent mechanical propertiesand adhesive properties.

1. A curable resin composition comprising: (A) an oxyalkylene polymer having silicon-containing functional groups crosslinkable through formation of siloxane bonds; (B) a copolymer having silicon-containing functional groups crosslinkable through formation of siloxane bonds, the molecular chain of the copolymer consisting substantially of (b-1) an alkyl (meth)acrylate monomeric unit having C₁–C₂ alkyl and (b-2) an alkyl (meth)acrylate monomeric unit having -alkyl selected from the group consisting of 2-ethylhexyl, isooctyl and isononyl; and (C) a curing agent.
 2. The curable resin composition according to claim 1, wherein the molecular chain of the polymer (A) consists substantially of a repeating unit represented by general formula (1): —CH(CH₃)CH₂—O—  (1)
 3. The curable resin composition according to claim 1 or 2, wherein the number-average molecular weight of the polymer (A) is at least 6,000 and Mw/Mn is 1.6 or less.
 4. The curable resin composition according to one of claims 1 to 3, wherein the main chain of the polymer of (A) is synthesized by polymerizing alkylene oxide in the presence of an initiator and at least one catalyst selected from the group consisting of a cyanide complex of compound metal, a cesium compound, and a compound containing a P═N bond. 